One of the challenges in designing a conferencing device is to ensure that a talker's voice will be detected and captured regardless of the talker's location relative to the device. For example, it is common for devices that incorporate non directional microphones to pick up room reverberation that obscures the voice of the talker. In conferencing devices having multiple microphones, it is conventional to rely on either directional microphones for talker localization or a full set of beam formers to isolate the active talker. For example, the UC360 Collaboration Point conferencing unit manufactured by Mitel Networks Corporation creates beams in multiple directions, as set forth, for example in U.S. Pat. No. 7,130,797, assigned to Mitel Networks Corporation, the contents of which are incorporated herein by reference.
Although beam forming techniques can be used for talker localization, beam forming requires the use of a filter for each microphone as well as a summer to mix the multiple microphone signals. For example, in a conferencing device having sixteen supported sectors there is a requirement for sixteen microphones and associated filters, which results in the wideband audio processing requirements becoming very large. Also, the asymmetric design of some conferencing devices can result in cavities that give rise to poor separation between sectors with the result that even when beam forming is used, the beam responses between adjacent sectors may overlap (and interfere with one another) significantly in certain frequency bands (e.g. between 600 Hz and 1450 Hz).
Non-symmetry of the device design, increased wideband audio processing requirements and increased sector count can result in a computational load that is too large to be handled efficiently or economically.